1CREATE INDEX(7) PostgreSQL 13.4 Documentation CREATE INDEX(7)
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6 CREATE_INDEX - define a new index
7
9 CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT EXISTS ] name ] ON [ ONLY ] table_name [ USING method ]
10 ( { column_name | ( expression ) } [ COLLATE collation ] [ opclass [ ( opclass_parameter = value [, ... ] ) ] ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ] [, ...] )
11 [ INCLUDE ( column_name [, ...] ) ]
12 [ WITH ( storage_parameter [= value] [, ... ] ) ]
13 [ TABLESPACE tablespace_name ]
14 [ WHERE predicate ]
15
17 CREATE INDEX constructs an index on the specified column(s) of the
18 specified relation, which can be a table or a materialized view.
19 Indexes are primarily used to enhance database performance (though
20 inappropriate use can result in slower performance).
21 The key field(s) for the index are specified as column names, or
23 alternatively as expressions written in parentheses. Multiple fields
24 can be specified if the index method supports multicolumn indexes.
25 An index field can be an expression computed from the values of one or
27 more columns of the table row. This feature can be used to obtain fast
28 access to data based on some transformation of the basic data. For
29 example, an index computed on upper(col) would allow the clause WHERE
30 upper(col) = 'JIM' to use an index.
31 PostgreSQL provides the index methods B-tree, hash, GiST, SP-GiST, GIN,
33 and BRIN. Users can also define their own index methods, but that is
34 fairly complicated.
35 When the WHERE clause is present, a partial index is created. A partial
37 index is an index that contains entries for only a portion of a table,
38 usually a portion that is more useful for indexing than the rest of the
39 table. For example, if you have a table that contains both billed and
40 unbilled orders where the unbilled orders take up a small fraction of
41 the total table and yet that is an often used section, you can improve
42 performance by creating an index on just that portion. Another possible
43 application is to use WHERE with UNIQUE to enforce uniqueness over a
44 subset of a table. See Section 11.8 for more discussion.
45 The expression used in the WHERE clause can refer only to columns of
47 the underlying table, but it can use all columns, not just the ones
48 being indexed. Presently, subqueries and aggregate expressions are also
49 forbidden in WHERE. The same restrictions apply to index fields that
50 are expressions.
51 All functions and operators used in an index definition must be
53 “immutable”, that is, their results must depend only on their arguments
54 and never on any outside influence (such as the contents of another
55 table or the current time). This restriction ensures that the behavior
56 of the index is well-defined. To use a user-defined function in an
57 index expression or WHERE clause, remember to mark the function
58 immutable when you create it.
59
61 UNIQUE
62 Causes the system to check for duplicate values in the table when
63 the index is created (if data already exist) and each time data is
64 added. Attempts to insert or update data which would result in
65 duplicate entries will generate an error.
66 Additional restrictions apply when unique indexes are applied to
68 partitioned tables; see CREATE TABLE (CREATE_TABLE(7)).
69 CONCURRENTLY
71 When this option is used, PostgreSQL will build the index without
72 taking any locks that prevent concurrent inserts, updates, or
73 deletes on the table; whereas a standard index build locks out
74 writes (but not reads) on the table until it's done. There are
75 several caveats to be aware of when using this option — see
76 Building Indexes Concurrently below.
77 For temporary tables, CREATE INDEX is always non-concurrent, as no
79 other session can access them, and non-concurrent index creation is
80 cheaper.
81 IF NOT EXISTS
83 Do not throw an error if a relation with the same name already
84 exists. A notice is issued in this case. Note that there is no
85 guarantee that the existing index is anything like the one that
86 would have been created. Index name is required when IF NOT EXISTS
87 is specified.
88 INCLUDE
90 The optional INCLUDE clause specifies a list of columns which will
91 be included in the index as non-key columns. A non-key column
92 cannot be used in an index scan search qualification, and it is
93 disregarded for purposes of any uniqueness or exclusion constraint
94 enforced by the index. However, an index-only scan can return the
95 contents of non-key columns without having to visit the index's
96 table, since they are available directly from the index entry.
97 Thus, addition of non-key columns allows index-only scans to be
98 used for queries that otherwise could not use them.
99 It's wise to be conservative about adding non-key columns to an
101 index, especially wide columns. If an index tuple exceeds the
102 maximum size allowed for the index type, data insertion will fail.
103 In any case, non-key columns duplicate data from the index's table
104 and bloat the size of the index, thus potentially slowing searches.
105 Furthermore, B-tree deduplication is never used with indexes that
106 have a non-key column.
107 Columns listed in the INCLUDE clause don't need appropriate
109 operator classes; the clause can include columns whose data types
110 don't have operator classes defined for a given access method.
111 Expressions are not supported as included columns since they cannot
113 be used in index-only scans.
114 Currently, the B-tree and the GiST index access methods support
116 this feature. In B-tree and the GiST indexes, the values of columns
117 listed in the INCLUDE clause are included in leaf tuples which
118 correspond to heap tuples, but are not included in upper-level
119 index entries used for tree navigation.
120 name
122 The name of the index to be created. No schema name can be included
123 here; the index is always created in the same schema as its parent
124 table. If the name is omitted, PostgreSQL chooses a suitable name
125 based on the parent table's name and the indexed column name(s).
126 ONLY
128 Indicates not to recurse creating indexes on partitions, if the
129 table is partitioned. The default is to recurse.
130 table_name
132 The name (possibly schema-qualified) of the table to be indexed.
133 method
135 The name of the index method to be used. Choices are btree, hash,
136 gist, spgist, gin, and brin. The default method is btree.
137 column_name
139 The name of a column of the table.
140 expression
142 An expression based on one or more columns of the table. The
143 expression usually must be written with surrounding parentheses, as
144 shown in the syntax. However, the parentheses can be omitted if the
145 expression has the form of a function call.
146 collation
148 The name of the collation to use for the index. By default, the
149 index uses the collation declared for the column to be indexed or
150 the result collation of the expression to be indexed. Indexes with
151 non-default collations can be useful for queries that involve
152 expressions using non-default collations.
153 opclass
155 The name of an operator class. See below for details.
156 opclass_parameter
158 The name of an operator class parameter. See below for details.
159 ASC
161 Specifies ascending sort order (which is the default).
162 DESC
164 Specifies descending sort order.
165 NULLS FIRST
167 Specifies that nulls sort before non-nulls. This is the default
168 when DESC is specified.
169 NULLS LAST
171 Specifies that nulls sort after non-nulls. This is the default when
172 DESC is not specified.
173 storage_parameter
175 The name of an index-method-specific storage parameter. See Index
176 Storage Parameters below for details.
177 tablespace_name
179 The tablespace in which to create the index. If not specified,
180 default_tablespace is consulted, or temp_tablespaces for indexes on
181 temporary tables.
182 predicate
184 The constraint expression for a partial index.
185 Index Storage Parameters
187 The optional WITH clause specifies storage parameters for the index.
188 Each index method has its own set of allowed storage parameters. The
189 B-tree, hash, GiST and SP-GiST index methods all accept this parameter:
190 fillfactor (integer)
192 The fillfactor for an index is a percentage that determines how
193 full the index method will try to pack index pages. For B-trees,
194 leaf pages are filled to this percentage during initial index
195 build, and also when extending the index at the right (adding new
196 largest key values). If pages subsequently become completely full,
197 they will be split, leading to gradual degradation in the index's
198 efficiency. B-trees use a default fillfactor of 90, but any integer
199 value from 10 to 100 can be selected. If the table is static then
200 fillfactor 100 is best to minimize the index's physical size, but
201 for heavily updated tables a smaller fillfactor is better to
202 minimize the need for page splits. The other index methods use
203 fillfactor in different but roughly analogous ways; the default
204 fillfactor varies between methods.
205 B-tree indexes additionally accept this parameter:
207 deduplicate_items (boolean)
209 Controls usage of the B-tree deduplication technique described in
210 Section 63.4.2. Set to ON or OFF to enable or disable the
211 optimization. (Alternative spellings of ON and OFF are allowed as
212 described in Section 19.1.) The default is ON.
213 Note
215 Turning deduplicate_items off via ALTER INDEX prevents future
216 insertions from triggering deduplication, but does not in
217 itself make existing posting list tuples use the standard tuple
218 representation.
219 GiST indexes additionally accept this parameter:
221 buffering (enum)
223 Determines whether the buffering build technique described in
224 Section 64.4.1 is used to build the index. With OFF it is disabled,
225 with ON it is enabled, and with AUTO it is initially disabled, but
226 turned on on-the-fly once the index size reaches
227 effective_cache_size. The default is AUTO.
228 GIN indexes accept different parameters:
230 fastupdate (boolean)
232 This setting controls usage of the fast update technique described
233 in Section 66.4.1. It is a Boolean parameter: ON enables fast
234 update, OFF disables it. The default is ON.
235 Note
237 Turning fastupdate off via ALTER INDEX prevents future
238 insertions from going into the list of pending index entries,
239 but does not in itself flush previous entries. You might want
240 to VACUUM the table or call gin_clean_pending_list function
241 afterward to ensure the pending list is emptied.
242 gin_pending_list_limit (integer)
244 Custom gin_pending_list_limit parameter. This value is specified in
245 kilobytes.
246 BRIN indexes accept different parameters:
248 pages_per_range (integer)
250 Defines the number of table blocks that make up one block range for
251 each entry of a BRIN index (see Section 67.1 for more details). The
252 default is 128.
253 autosummarize (boolean)
255 Defines whether a summarization run is invoked for the previous
256 page range whenever an insertion is detected on the next one.
257 Building Indexes Concurrently
259 Creating an index can interfere with regular operation of a database.
260 Normally PostgreSQL locks the table to be indexed against writes and
261 performs the entire index build with a single scan of the table. Other
262 transactions can still read the table, but if they try to insert,
263 update, or delete rows in the table they will block until the index
264 build is finished. This could have a severe effect if the system is a
265 live production database. Very large tables can take many hours to be
266 indexed, and even for smaller tables, an index build can lock out
267 writers for periods that are unacceptably long for a production system.
268 PostgreSQL supports building indexes without locking out writes. This
270 method is invoked by specifying the CONCURRENTLY option of CREATE
271 INDEX. When this option is used, PostgreSQL must perform two scans of
272 the table, and in addition it must wait for all existing transactions
273 that could potentially modify or use the index to terminate. Thus this
274 method requires more total work than a standard index build and takes
275 significantly longer to complete. However, since it allows normal
276 operations to continue while the index is built, this method is useful
277 for adding new indexes in a production environment. Of course, the
278 extra CPU and I/O load imposed by the index creation might slow other
279 operations.
280 In a concurrent index build, the index is actually entered into the
282 system catalogs in one transaction, then two table scans occur in two
283 more transactions. Before each table scan, the index build must wait
284 for existing transactions that have modified the table to terminate.
285 After the second scan, the index build must wait for any transactions
286 that have a snapshot (see Chapter 13) predating the second scan to
287 terminate, including transactions used by any phase of concurrent index
288 builds on other tables. Then finally the index can be marked ready for
289 use, and the CREATE INDEX command terminates. Even then, however, the
290 index may not be immediately usable for queries: in the worst case, it
291 cannot be used as long as transactions exist that predate the start of
292 the index build.
293 If a problem arises while scanning the table, such as a deadlock or a
295 uniqueness violation in a unique index, the CREATE INDEX command will
296 fail but leave behind an “invalid” index. This index will be ignored
297 for querying purposes because it might be incomplete; however it will
298 still consume update overhead. The psql \d command will report such an
299 index as INVALID:
300 postgres=# \d tab
302 Table "public.tab"
303 Column | Type | Collation | Nullable | Default
304 --------+---------+-----------+----------+---------
305 col | integer | | |
306 Indexes:
307 "idx" btree (col) INVALID
308 The recommended recovery method in such cases is to drop the index and
310 try again to perform CREATE INDEX CONCURRENTLY. (Another possibility is
311 to rebuild the index with REINDEX INDEX CONCURRENTLY).
312 Another caveat when building a unique index concurrently is that the
314 uniqueness constraint is already being enforced against other
315 transactions when the second table scan begins. This means that
316 constraint violations could be reported in other queries prior to the
317 index becoming available for use, or even in cases where the index
318 build eventually fails. Also, if a failure does occur in the second
319 scan, the “invalid” index continues to enforce its uniqueness
320 constraint afterwards.
321 Concurrent builds of expression indexes and partial indexes are
323 supported. Errors occurring in the evaluation of these expressions
324 could cause behavior similar to that described above for unique
325 constraint violations.
326 Regular index builds permit other regular index builds on the same
328 table to occur simultaneously, but only one concurrent index build can
329 occur on a table at a time. In either case, schema modification of the
330 table is not allowed while the index is being built. Another difference
331 is that a regular CREATE INDEX command can be performed within a
332 transaction block, but CREATE INDEX CONCURRENTLY cannot.
333 Concurrent builds for indexes on partitioned tables are currently not
335 supported. However, you may concurrently build the index on each
336 partition individually and then finally create the partitioned index
337 non-concurrently in order to reduce the time where writes to the
338 partitioned table will be locked out. In this case, building the
339 partitioned index is a metadata only operation.
340
342 See Chapter 11 for information about when indexes can be used, when
343 they are not used, and in which particular situations they can be
344 useful.
345 Currently, only the B-tree, GiST, GIN, and BRIN index methods support
347 multicolumn indexes. Up to 32 fields can be specified by default. (This
348 limit can be altered when building PostgreSQL.) Only B-tree currently
349 supports unique indexes.
350 An operator class with optional parameters can be specified for each
352 column of an index. The operator class identifies the operators to be
353 used by the index for that column. For example, a B-tree index on
354 four-byte integers would use the int4_ops class; this operator class
355 includes comparison functions for four-byte integers. In practice the
356 default operator class for the column's data type is usually
357 sufficient. The main point of having operator classes is that for some
358 data types, there could be more than one meaningful ordering. For
359 example, we might want to sort a complex-number data type either by
360 absolute value or by real part. We could do this by defining two
361 operator classes for the data type and then selecting the proper class
362 when creating an index. More information about operator classes is in
363 Section 11.10 and in Section 37.16.
364 When CREATE INDEX is invoked on a partitioned table, the default
366 behavior is to recurse to all partitions to ensure they all have
367 matching indexes. Each partition is first checked to determine whether
368 an equivalent index already exists, and if so, that index will become
369 attached as a partition index to the index being created, which will
370 become its parent index. If no matching index exists, a new index will
371 be created and automatically attached; the name of the new index in
372 each partition will be determined as if no index name had been
373 specified in the command. If the ONLY option is specified, no recursion
374 is done, and the index is marked invalid. (ALTER INDEX ... ATTACH
375 PARTITION marks the index valid, once all partitions acquire matching
376 indexes.) Note, however, that any partition that is created in the
377 future using CREATE TABLE ... PARTITION OF will automatically have a
378 matching index, regardless of whether ONLY is specified.
379 For index methods that support ordered scans (currently, only B-tree),
381 the optional clauses ASC, DESC, NULLS FIRST, and/or NULLS LAST can be
382 specified to modify the sort ordering of the index. Since an ordered
383 index can be scanned either forward or backward, it is not normally
384 useful to create a single-column DESC index — that sort ordering is
385 already available with a regular index. The value of these options is
386 that multicolumn indexes can be created that match the sort ordering
387 requested by a mixed-ordering query, such as SELECT ... ORDER BY x ASC,
388 y DESC. The NULLS options are useful if you need to support “nulls sort
389 low” behavior, rather than the default “nulls sort high”, in queries
390 that depend on indexes to avoid sorting steps.
391 The system regularly collects statistics on all of a table's columns.
393 Newly-created non-expression indexes can immediately use these
394 statistics to determine an index's usefulness. For new expression
395 indexes, it is necessary to run ANALYZE or wait for the autovacuum
396 daemon to analyze the table to generate statistics for these indexes.
397 For most index methods, the speed of creating an index is dependent on
399 the setting of maintenance_work_mem. Larger values will reduce the time
400 needed for index creation, so long as you don't make it larger than the
401 amount of memory really available, which would drive the machine into
402 swapping.
403 PostgreSQL can build indexes while leveraging multiple CPUs in order to
405 process the table rows faster. This feature is known as parallel index
406 build. For index methods that support building indexes in parallel
407 (currently, only B-tree), maintenance_work_mem specifies the maximum
408 amount of memory that can be used by each index build operation as a
409 whole, regardless of how many worker processes were started. Generally,
410 a cost model automatically determines how many worker processes should
411 be requested, if any.
412 Parallel index builds may benefit from increasing maintenance_work_mem
414 where an equivalent serial index build will see little or no benefit.
415 Note that maintenance_work_mem may influence the number of worker
416 processes requested, since parallel workers must have at least a 32MB
417 share of the total maintenance_work_mem budget. There must also be a
418 remaining 32MB share for the leader process. Increasing
419 max_parallel_maintenance_workers may allow more workers to be used,
420 which will reduce the time needed for index creation, so long as the
421 index build is not already I/O bound. Of course, there should also be
422 sufficient CPU capacity that would otherwise lie idle.
423 Setting a value for parallel_workers via ALTER TABLE (ALTER_TABLE(7))
425 directly controls how many parallel worker processes will be requested
426 by a CREATE INDEX against the table. This bypasses the cost model
427 completely, and prevents maintenance_work_mem from affecting how many
428 parallel workers are requested. Setting parallel_workers to 0 via ALTER
429 TABLE will disable parallel index builds on the table in all cases.
430 Tip
432 You might want to reset parallel_workers after setting it as part
433 of tuning an index build. This avoids inadvertent changes to query
434 plans, since parallel_workers affects all parallel table scans.
435 While CREATE INDEX with the CONCURRENTLY option supports parallel
437 builds without special restrictions, only the first table scan is
438 actually performed in parallel.
439 Use DROP INDEX (DROP_INDEX(7)) to remove an index.
441 Like any long-running transaction, CREATE INDEX on a table can affect
443 which tuples can be removed by concurrent VACUUM on any other table.
444 Prior releases of PostgreSQL also had an R-tree index method. This
446 method has been removed because it had no significant advantages over
447 the GiST method. If USING rtree is specified, CREATE INDEX will
448 interpret it as USING gist, to simplify conversion of old databases to
449 GiST.
450
452 To create a unique B-tree index on the column title in the table films:
453 CREATE UNIQUE INDEX title_idx ON films (title);
455 To create a unique B-tree index on the column title with included
457 columns director and rating in the table films:
458 CREATE UNIQUE INDEX title_idx ON films (title) INCLUDE (director, rating);
460 To create a B-Tree index with deduplication disabled:
462 CREATE INDEX title_idx ON films (title) WITH (deduplicate_items = off);
464 To create an index on the expression lower(title), allowing efficient
466 case-insensitive searches:
467 CREATE INDEX ON films ((lower(title)));
469 (In this example we have chosen to omit the index name, so the system
471 will choose a name, typically films_lower_idx.)
472 To create an index with non-default collation:
474 CREATE INDEX title_idx_german ON films (title COLLATE "de_DE");
476 To create an index with non-default sort ordering of nulls:
478 CREATE INDEX title_idx_nulls_low ON films (title NULLS FIRST);
480 To create an index with non-default fill factor:
482 CREATE UNIQUE INDEX title_idx ON films (title) WITH (fillfactor = 70);
484 To create a GIN index with fast updates disabled:
486 CREATE INDEX gin_idx ON documents_table USING GIN (locations) WITH (fastupdate = off);
488 To create an index on the column code in the table films and have the
490 index reside in the tablespace indexspace:
491 CREATE INDEX code_idx ON films (code) TABLESPACE indexspace;
493 To create a GiST index on a point attribute so that we can efficiently
495 use box operators on the result of the conversion function:
496 CREATE INDEX pointloc
498 ON points USING gist (box(location,location));
499 SELECT * FROM points
500 WHERE box(location,location) && '(0,0),(1,1)'::box;
501 To create an index without locking out writes to the table:
503 CREATE INDEX CONCURRENTLY sales_quantity_index ON sales_table (quantity);
505
507 CREATE INDEX is a PostgreSQL language extension. There are no
508 provisions for indexes in the SQL standard.
509
511 ALTER INDEX (ALTER_INDEX(7)), DROP INDEX (DROP_INDEX(7)), REINDEX(7)
512PostgreSQL 13.4 2021 CREATE INDEX(7)